I had 2 experiences, both were third party policies bought from the dealer where I bought the car from.

The first was a success, I think because the dealer stayed in business for the term of the policy. All calls were directly to the dealer with no problems. I had an axle and trans issue fixed for the stated deductible.

The second, the dealer went out of business and was bought by an out of town dealer, then they shut down that local dealer (the other out of town dealer was still in business). My policy was still in effect. I had a carb to intake manifold gasket go out, and had it repaired by another dealer. I had to go through a call center in Texas and they wanted to see all my oil change records before authorizing the repair. I explained I did all the required manifold gasket maintenance.. 3 months later I finally beat them down enough to pay most of the bill. It was not easy.

Neither of these policies were from the auto manufacturer ( Ford and Isuzu). I think a CPO policy would probably be easier to get cooperation.